#include <iostream>

using namespace std;

int a[1001][1001], n;
int main()
{
    cin >> n;
    for (int i=1; i<=n; i++)
        {
            for(int j=1; j<=i; j++)
                {
                    cin >> a[i][j];
                }
        }

    for (int i=n-1; i>=1; i--)
        {
            for (int j=1; j<=i; j++)
                {
                    if (a[i+1][j]>=a[i+1][j+1])
                        {
                            a[i][j]+=a[i+1][j];
                        }
                    else
                        {
                            a[i][j]+= a[i+1][j+1];
                        }
                }
        }

    cout << a[1][1];
    return 0;
}
